Transmission device, reception device, communication system, and communication method

ABSTRACT

A transmission device that generates control information including 3-bit information and transmits a physical downlink shared channel, a reference signal for demodulation of the physical downlink shared channel, and the control information, wherein, in a case that all codewords which are mapped to the physical downlink shared channel are enabled, among a first value to an eighth value indicated by the 3-bit information, the third value to the eighth value indicate that the number of layers is from 3 to 8 respectively, and the first value and the second value indicate that the number of layers is equal to 2, and the first value indicates that the scrambling identity for the reference signal is equal to 0 and the second value indicates that the scrambling identity is equal to 1.

This application is a Continuation of copending application Ser. No.14/339,145, filed on Jul. 23, 2014, which is a continuation ofapplication Ser. No. 13/574,516, filed on Jul. 20, 2012, now U.S. Pat.No. 8,995,550 B2, which is the National Phase of PCT InternationalApplication No. PCT/JP2011/050642 filed on Jan. 17, 2011, which claimsthe benefit under 35 U.S.C. §119(a) to Patent Application No.2010-011868, filed in Japan on Jan. 22, 2010, all of which are herebyexpressly incorporated by reference into the present application.

TECHNICAL FIELD

The present invention relates to a transmission device, a receptiondevice, a communication system, and a communication method.

BACKGROUND ART

There are known mobile radio communication systems such as WCDMA(Wideband Code Division Multiple Access), LTE (Long Term Evolution),LTE-A (LTE-Advanced, and WiMAX (Worldwide Interoperability for MicrowaveAccess) by 3GPP (Third Generation Partnership Project). These mobileradio communication systems can increase the communication area by acellular configuration in which the area covered by a base station (abase station device, a transmission station, a transmission device,eNodeB) or a transmission station conforming to the base station isarranged as a plurality of cells.

The aforementioned mobile radio communication system can realize a moreefficient data transmission by adaptively controlling the modulation andcoding scheme (MCS), the number of spatial multiplex (layers, rank),precoding weight (precoding matrix) and the like according to thecommunication path status between abase station and a terminal device.NPL 1 net forth below discloses a method of such control.

FIG. 17 represents an example of a SU (Single User)-MIMO (Multiple InputMultiple Output, spatial multiplex transmission) in a transmission modeusing the dual layer beam forming scheme of LTE. A base station 1701transmits two transmission data addressed to a terminal device 1702,i.e. transmission data 1703 and transmission data 1704, using two ports(logic ports) that are spatial-multiplex for a terminal device 1702,i.e. a port 7 and a port 8. A reference signal of port 7 and a referencesignal of port 8 are multiplied by spread codes orthogonal to eachother. Accordingly, terminal device 1702 can readily have the referencesignal of port 7 and the reference signal of port 8 separated.

FIG. 18 represents an example of downlink multiple user (MU)-MIMO in atransmission mode using a dual layer beam forming scheme of LTE. A basestation 1801 uses port 7 and port 8 that are two spatial-multiplexedports, as disclosed in NPL 2 set forth below, to transmit transmissiondata 1804 addressed to a terminal device 1802 and transmission data 1805addressed to a terminal device 1803 at the same time and using the samefrequency towards terminal devices 1802 and 1803. The reference signalof port 7 and the reference signal of port 8 are multiplied by spreadcodes orthogonal to each other. The terminal device is configured toidentify in which port its own addressed transmission data is includedby using downlink control information. Terminal device 1802 and terminaldevice 1803 can readily separate the reference signal of port 7 and thereference signal of port 8. Furthermore, terminal device 1802 andterminal device 1803 can extract the transmission data by demodulatingthe received data using a reference signal corresponding to its ownaddressed port.

FIG. 19 represents another example of downlink MU-MIMO transmission in atransmission mode using a dual layer beam forming scheme of LTE. A basestation 1901 uses port 7 that is one of the two ports that arespatial-multiplexed for a terminal device 1902 and a terminal device1903 to transmit transmission data 1904 addressed to terminal device1902 and transmission data 1905 addressed to terminal device 1903 at thesame time and using the same frequency. Although base station 1901 sendstransmission data 1904 and transmission data 1905 through the same port7, the directivity of the signals for sending respective transmissiondata can be set independently. Specifically, base station 1901 sendstransmission data 1904 in a first directivity 1906 and transmission data1905 in a second directivity 1907. The reference signal for terminaldevice 1902 and the reference signal for terminal device 1903 aremultiplied by scrambling codes quasi-orthogonal to each other. Basestation 1901 notifies terminal device 1902 and terminal device 1903about information indicating respective scrambling codes throughdownlink control information. Accordingly, terminal device 1902 andterminal device 1903 can separate the reference signal of its own port 7using the difference in directivity and difference in the scramblingcode.

FIG. 20 represents a part of downlink control information in LTE. A codeword (CW) is a group of transmission data. The control informationincludes, in addition to the 16 bits of information related to CW1 andCW2 that are code words, a 1-bit scrambling code identification (SCID)indicating the type of scrambling code, as disclosed in NPL 3 set forthbelow. For each CW, a MCS (modulation and coding scheme) indicator(MCSI) indicating the MCS is represented in 5 bits, a new data indicator(NDI) indicating whether the transmission is the initial delivery or notis represented in 1 bit, and the redundancy version (RV) indicating thepuncturing pattern is represented in 2 bits.

In LTE, the CW addressed to four terminal devices at most can betransmitted by MU-MIMO relative to the two ports shown in FIG. 18 bymultiplying the two scrambling codes according to the 1-bit SCID shownin FIG. 20 by each port, as shown in FIG. 19.

In LTE-A that is an extended version of LTE, there is proposedincreasing the highest multiplex value of SU-MIMO to 8 while keeping thebackward compatibility to LTE, as described in NPL 4 set forth below.

CITATION LIST Non Patent Literatures

NPL 1: 3rd Generation Partnership Project (3GPP); TechnicalSpecification Group (TSG) Radio Access Network (RAN); Evolved UniversalTerrestrial Radio Access (E-UTRA); Physical Layer Procedures (Release8), December 2008, 3GPP TS 36.213 V8.8.0 (2009-September)

NPL 2: 3GPP TSG-RAN WG1 #58bis R1-094413, “Way forward on the details ofDCI format 213 for enhanced DL transmission”, October 2009

NPL 3: 3GPP TSG-RAN WGI #58bis R1-094408, “Way forward on DMRS sequencegeneration for dual layer SM”, October 2009

NPL 4: 3GPP TR 36.814 “Further Advancements for E-UTRA Physical LayerAspects”, December 2009

SUMMARY OF INVENTION Technical Problem

The signaling in a conventional system cannot accommodate more portsthan the number of ports expected in the conventional system. It wasdifficult to extend the ports, impeding improvement in the transmissionefficiency.

In view of the foregoing, an object of the present invention is toprovide a transmission device, a reception device, a communicationsystem and a communication method that can realize high transmissionefficiency by allowing extension to more ports than the conventionalnumber of ports through efficient signaling.

Solution to Problem

(1) An aspect of the present invention is directed to a transmissiondevice in a communication system in which a highest rank that is thenumber of spatial multiplex is 8. The transmission device includes acontrol information generation unit generating control informationincluding 3-bit rank information indicating the rank of transmissiondata, and a transmission unit transmitting the transmission data, areference signal that is a signal for demodulating a physical downlinkshared channel having the transmission data mapped, and the controlinformation.

(2) Preferably, among a first state to an eighth state represented bythe 3-bit rank information, the third state to eighth state indicatethat the rank is from 3 to 8, respectively, and the first state andsecond state indicate that the rank is less than or equal to 1 The firststate indicates that a sequence by which the reference signal ismultiplied is the first sequence, and the second state indicates that asequence by which the reference signal is multiplied is the secondsequence.

(3) Another aspect of the present invention is directed to a receptiondevice in a communication system in which a highest rank that is thenumber of spatial multiplex is 8. The reception device includes areception unit receiving transmission data, a reference signal that is asignal for demodulating a physical downlink shared channel having thetransmission data mapped, and control information including 3-bit rankinformation indicating the rank of the transmission data, and anidentification unit identifying a reference signal using the controlinformation.

(4) Preferably, among a first state to an eighth state represented bythe 3-bit rank information, the third state to eighth state indicatethat the rank is from 3 to 8, respectively, and the first state andsecond state indicate that the rank is less than or equal to 2. Thefirst state indicates that a sequence by which the reference signal ismultiplied is the first sequence, and the second state indicates that asequence by which the reference signal is multiplied is the secondsequence.

(5) Still another aspect of the present invention is directed to acommunication system in which a highest rank that is the number ofspatial multiplex of transmission data transmitted from a transmissiondevice to a reception device is 8. The transmission device includes acontrol information generation unit generating control informationincluding 3-bit rank information indicating the rank of transmissiondata, and a transmission unit transmitting transmission data, areference signal that is a signal for demodulating a physical downlinkshared channel having transmission data mapped, and control information.The reception device includes a reception unit receiving transmissiondata, a reference signal, and control information, and an identificationunit identifying the reference signal using control information.

(6) Preferably, among a first state to an eighth state represented bythe 3-bit rank information, the third state to eighth state indicatethat the rank is from 3 to 8, respectively, and the first state andsecond state indicate that the rank is less than or equal to 2. Thefirst state indicates that the sequence by which the reference signal ismultiplied is the first sequence, and the second state indicates thatthe sequence by which the reference signal is multiplied is the secondsequence.

(7) A still further aspect of the present invention is directed to acommunication method used at a transmission device in a communicationsystem in which a highest rank that is the number of spatial multiplexis 8. The communication method includes the steps of: the transmissiondevice generating control information including 3-bit rank informationindicating the rank of transmission data, and transmitting thetransmission data, a reference signal that is a signal for demodulatinga physical downlink shared channel having the transmission data mapped,and the control information.

(8) Preferably, among a first state to an eighth state represented bythe 3-bit rank information, the third state to eighth state indicatethat the rank is from 3 to 8, respectively, and the first state andsecond state indicate that the rank is less than or equal to 2. Thefirst state indicates that the sequence by which the reference signal ismultiplied is the first sequence, and the second state indicates thatthe sequence by which the reference signal is multiplied is the secondsequence.

(9) A still further aspect of the present invention is directed to acommunication method used at a reception device in a communicationsystem in which a highest rank that is the number of spatial multiplexis 8. The communication method includes the steps of: the receptiondevice receiving transmission data, a reference signal that is a signalfor demodulating a physical downlink shared channel having transmissiondata mapped, and control information including 3-bit rank informationindicating the rank of transmission data, and identifying the referencesignal using the control information.

(10) Preferably, among a first state to an eighth state represented bythe 3-bit rank information, the third state to eighth state indicatethat the rank is from 3 to 8, respectively, and the first state andsecond state indicate that the rank is less than or equal to 2. Thefirst state indicates that the sequence by which the reference signal ismultiplied is the first sequence, and the second state indicates thatthe sequence by which the reference signal is multiplied is the secondsequence.

Advantageous Effects of Invention

According to the present invention, high transmission efficiency can berealized by allowing extension to more ports than the conventionalnumber of ports through efficient signaling.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic view of a configuration of a communication systemaccording to a first embodiment of the present invention.

FIG. 2 is a schematic view of a configuration of a communication systemaccording to the first embodiment.

FIG. 3 is a schematic view of a configuration of a communication systemaccording to the first embodiment.

FIG. 4 is a schematic view of a configuration of a communication systemaccording to the first embodiment.

FIG. 5 represents an example of a radio frame configuration in the firstembodiment.

FIG. 6 represents an example of a resource block configuration in thefirst embodiment.

FIG. 7 represents an example of a resource block configuration in thefirst embodiment.

FIG. 8 represents an example of a resource block configuration in thefirst embodiment.

FIG. 9 represents a correspondence table of control information and thenumber of bits in the first embodiment.

FIG. 10 represents a correspondence table of control information andports in the first embodiment.

FIG. 11 represents a correspondence table of control information withports and sequences according to a second embodiment of the presentinvention.

FIG. 12 represents a correspondence table of control information and thenumber of bits according to a third embodiment of the present invention.

FIG. 13 represents a correspondence table of control information andports in the third embodiment.

FIG. 14 represents a correspondence table of control information withports and sequences according to the third embodiment.

FIG. 15 schematically represents an example of a configuration of a basestation (transmission device) according to the second embodiment of thepresent invention.

FIG. 16 schematically represents an example of a configuration of aterminal device (reception device) according to the second embodiment.

FIG. 17 represents a configuration of a communication system carryingout SU-MIMO communication.

FIG. 18 represents a configuration of a communication system carryingout MU-MIMO communication.

FIG. 19 represents a configuration of a communication system carryingout MU-MIMO communication.

FIG. 20 represents a correspondence table of control information withthe number of bits in a communication system carrying out MIMOcommunication.

DESCRIPTION OF EMBODIMENTS

Each of the embodiments of the present invention will be describedhereinafter with reference to the drawings. In the description set forthbelow, the same elements have the same reference characters allotted.Their designation and function are also the same, Therefore, detaileddescription thereof will not be repeated.

First Embodiment

A first embodiment of the present invention will be describedhereinafter with reference to the drawings.

FIG. 1 is a schematic diagram representing a configuration of acommunication system according to the first embodiment of the presentinvention. The communication system in FIG. 1 includes a base station101 (a transmission device, base station device, eNodeB, eNB, cell,uplink reception device) constituting a cell #1, and terminal devices102, 103, 104 and 105 (a reception device, UE, uplink transmissiondevice). Base station 101 transmits CWs 106, 107, 108 and 109 that aretransmission data for terminal devices 102, 103, 104 and 105,respectively, through MU-MIMO spatial multiplexing. The port for MU-MIMOcorresponds to four ports from port 7 to port 10. Therefore, basestation 101 can apply MU-MIMO multiplexing to the CW addressed to fourterminal devices at most. The first embodiment corresponds to the casewhere CWs 106, 107, 108 and 109 are transmitted using ports 7, 8, 9 and10, respectively. Base station 101 transmits to each terminal device thecontrol information to identify the port used for transmitting the CWaddressed to the relevant terminal device.

FIG. 2 represents the case where base station 101 applies MU-MIMOmultiplexing to the CWs addressed to the three terminal devices of 202,203 and 204 for transmission. Base station 101 transmits CW 205 and CW206 addressed to terminal devices 202 and 203, respectively, using ports7 and 8, respectively. Base station 101 further applies SU-MIMO to thetwo CWs addressed to terminal device 204 for transmission. Base station101 transmits CWs 207 and 208 that are transmission data addressed toterminal device 204 using ports 9 and 10 identical to the ports forMU-MIMO in FIG. 1. Base station 101 transmits to each terminal devicethe control information for identifying the port used for transmittingthe CW addressed to the relevant terminal device.

FIG. 3 represents the case where base station 101 applies SU-MIMOmultiplexing to the CW addressed to one terminal device 302. Basestation 101 transmits CWs 303 and 304 addressed to terminal device 302using port 7 and ports 8 and 9, respectively. Base station 101 transmitsto terminal device 302 the control information for identifying the portused for transmitting the CW addressed to that terminal device.

FIG. 4 represents the case where base station 101 applies SU-MIMOmultiplexing to the CW addressed to one terminal device 402 fortransmission. Base station 101 transmits CW 403 addressed to terminaldevice 402 using ports 7-10, and CW 404 addressed to terminal device 402using ports 11-14. Base station 101 transmits to terminal device 402 thecontrol information for identifying the port used for transmission ofthe CW addressed to that terminal device.

Ports 7-10 are shared between SU-MIMO and MU-MIMO. Accordingly, themutual information related to ports between the base station andterminal device (agreement made in advance) can be simplified. Thismutual information will be described in detail afterwards.

FIG. 5 schematically represents a downlink radio frame configuration inthe present embodiment. In FIG. 5, the time and frequency are plottedalong the horizontal axis and vertical axis, respectively. In the timeaxis, a radio frame is 10 ms, One radio frame includes 10 subframes.Each subframe includes two slots. Each slot includes seven orthogonalfrequency division multiplex (OFDM) symbols. On the frequency axis,multiple subcarriers are arranged at the interval of 15 kHz, A unitincluding 1 slot in the direction of the time axis and 12 subcarriers inthe direction of the frequency axis constitutes a resource block (RB).This RB is the allocation unit of transmission data. In the case ofSU-MIMO, a plurality of CWs are spatial multiplexed and allocated usinga plurality of ports to one or multiple RBs. In the case of MU-MIMO, CWaddressed to a plurality of terminal devices are spatial multiplexed andallocated using a plurality of ports to one or multiple RBs. Eachsubframe includes a physical downlink control channel that is a regionwhere downlink control information is mapped, a physical downlink sharedchannel PDSCH for mapping downlink transmission data, and a RS(reference signal, demodulation reference signal (DM-RS), UE referencesignal (UE-RS) that is a reference signal for demodulation of PDSCH.

RS is a reference signal unique to a terminal device. RS is subjected toprecoding similar to that of PDSCH to which transmission data addressedto that terminal device is allocated. RS is inserted into an RBallocated to the transmission data addressed to that terminal device, RSis used for MIMO separation and demodulation of PDSCH. RS is setindividually for each port. RS is inserted so as to be orthogonal toeach other between ports. When the number of ports used differs betweenRBs, the inserted number of RSs also differs. For the multiplexingmethod of RS between ports, time division multiplexing (TDM) mapping toindependent OFDM symbols, frequency-division multiplexing (FDM) mappingto independent subcarriers, and code division multiplexing (CDM)multiplying an independent spread code may be employed. Alternatively,such multiplexing method may be used in combination.

The case where FDM and CDM are used together as the multiplexing methodof RS between ports will be described hereinafter. FIG. 6 represents thedetails of two RBs aligned on the time axis in FIG. 5. As mentionedabove, 7 OFDM symbols on the time axis and 12 subcarriers on thefrequency axis constitute one RB. One RB includes 84 resource elements(RE), each being a region constituted of 1 OFDM symbol and 1 subcarrier.FIG. 6 represents the RS arrangement when there is one port (port 7) ortwo ports (port 7 and port 8). The 12 REs identified by the hatchedregions in FIG. 6 are the REs where RS is mapped. hi the case of oneport, base station 101 maps the sequence for port 7 to the 12 REsidentified by the hatched regions. When there are two ports, basestation 101 maps the independent sequences for port 7 and port 8 to the12 REs identified by the hatched regions. The independent sequences forport 7 and port 8 are configured to be multiplexed by CDM with aspreading factor of 2 between two adjacent REs 601 in which RS ismapped, and demultiplexed at the terminal device side.

FIG. 7 represents the RS arrangement when there are three ports (port 7,port 8 and port 9) or four ports (port 7, port 8, port 9 and port 10).The 24 REs identified by the hatched regions (12 diagonally left-downhatched regions and 12 diagonally right-down regions) is the REs inwhich RS is mapped. When there are three ports, base station 101 mapsthe sequence for port 9, in addition to port 7 and port 8 shown in FIG.6, to the 12 REs identified by the diagonally right-down hatchedregions. In other words, port 7 (port 8) and port 9 are multiplexed byFDM. When there are four ports, base station 101 maps independentsequences for port 9 and for port 10 to the 12 REs identified by thediagonally right-down hatched regions. Here, independent sequences forport 9 and for port 10 are configured to be multiplexed by CDM with aspreading factor of 2 between two adjacent REs 701 in which RS ismapped, and demultiplexed at the terminal device side. Although thedescription is based on the case where port 9 and port 10 are used inaddition to ports 7 and 8, ports 7 and 8 do not necessarily have to bemapped when only ports 9 and 10 are used.

FIG. 8 represents the RS arrangement when there are eight ports (ports7-14). The 24 REs identified by the hatched regions (12 diagonallyleft-down hatched regions and 12 diagonally right-down regions) are theREs in which RS is mapped. Base station 101 maps the independentsequences for port 7 to port 10 to the 12 REs identified by thediagonally left-down hatched regions. Here, the independent sequencesfor port 7 to port 10 are configured to be multiplexed by 4-spread CDMbetween 4 REs 801 on the same frequency in which RS is mapped, anddemultiplexed at the terminal device side. Base station 101 maps theindependent sequences for port 11 to port 14 to the 12 REs identified bythe diagonally right-down hatched regions. Here, the independentsequences for port 11 to port 14 are configured to be multiplexed by4-spread CDM between 4 REs 802 on the same frequency in which RS ismapped, and demultiplexed at the terminal device side. The sequence ofeach port in FIGS. 6-8 can be obtained by multiplying an orthogonal codesequence and a quasi-orthogonal code sequence.

Base station 101 can carry out signaling (notification of controlinformation) efficiently by (a) setting a lower of the maximum number ofports for MU-MIMO as compared to the maximum number of ports forSU-MIMO, (b) sharing the port used in MU-MIMO with the port used inSU-MIMO, and (c) using common RS mapping or sequence between MU-MIMO andSU-IMO at the shared port. Furthermore, since the format of the controlinformation can be shared, base station 101 can dynamically switchbetween SU-MIMO and MU-MIMO. Thus, base station 101 can improve theusage efficiency of frequency by adaptive switching.

Specific signaling will be described hereinafter. FIG. 9 represents anexample of control information involved in the present embodiment. Basestation 101 supporting as many as 8 ports in SU-MIMO notifies eachterminal device about control information including the informationshown in FIG. 9. Specifically, the control information includes 3 bitsfor rank information (first identifier, spatial multiplex information)indicating the number of spatial multiplex addressed to that terminaldevice, and 16 bits of information related to CW1 and CW2 (secondidentifier, information indicating the parameter related to transmissiondata), for each terminal device. For each CW. MCSI indicating MCS isrepresented by 5 bits, NDI indicating whether the transmission is theinitial delivery or not is represented by 1 bit, and RV indicating thepuncturing pattern is represented by 2 bits. A predetermined combinationof MCSI and RV indicates that the relevant CW is non-transmission (nottransmitted), As a specific example, non-transmission can be indicatedwhen MCSI is the MCS of the lowest transmission rate and RV indicatespuncturing in retransmission.

FIG. 10 represents a correspondence table showing ports corresponding ocontrol information according to the present embodiment. Among the 8states represented by the 3-bit rank information, state 1 and state 2both indicate that the rank is rank 2 or lower. For those of state 3 andabove among the 8 states, the number of each state corresponds to therank number.

When the rank information is at state 1 or state 2, base station 101specifies a port using the state allocated to the information for everyCW, in addition to the rank information. When one CW is to betransmitted to an arbitrary terminal device, base station 101 sets theMCSI and RV combination of one CW at “disable” (combination indicatingnon-transmission) and the MCSI and RV combination of the other CW at“enable” (combination of arbitrary values that are not “disable”). Basedon the 1-bit NDI at the CW set at “disable” and whether the rankinformation is at state 1 or state 2, base station 101 specifies thefour ports of port 7-12.

When two CWs are to be transmitted towards an arbitrary terminal device,base station 101 sets the MCSI and RV combination of both CWs at“enable”. Base station 101 specifies the combination of port 7 and port8, or the combination of port 9 and port 10, depending upon whether therank information is at state 1 or state 2. On part of the terminaldevice, first the rank information is confirmed. The terminal deviceconfirms the MCSI and RV combination of CW1 and CW2 when the rankinformation is at state 1 or state 2. When both are “enable”, theterminal device obtains the two ports information from the state of therank information. If the MCSI and RV combination of one CW is “disable”,the terminal device confirms the NDI and SCID of the CW corresponding to“disable”, and obtains one port information. Although FIG. 3 shows thecase where CW1 is used in transmitting one CW towards one terminaldevice, the MCSI and RV combination and the NDI of CW1 are to bereplaced with those of CW2 when CW2 is to be used. State 1 and state 2can be shared between SU-MIMO and MU-MIMO.

When the rank information is at state 3 to state 8, base station 101specifies the port combination using each state. By setting the highestmultiplex value of the data addressed to one terminal device at 2 inMU-MIMO, it can be implicitly stated that state 3 to state 8 areSU-MIMO. Furthermore, by fixedly setting the employed port for each rankof SU-MIMO by base station 101, the rank information state and portcombination can be set in one-to-one correspondence. Thus, base station101 can suppress the number of bits required for the controlinformation.

For example, for a terminal device transmitting one CW using port 7 suchas terminal device 102 in FIG. 1 and terminal device 202 in FIG. 2, basestation 101 sets the rank information in the control information at 1,sets “enable” for the MCSI and RV combination of CW1, and “disable” forthe MCSI and RV combination of CW2, and the NDI of CW2 at 0. For aterminal device transmitting two CWs using port 9 and port 10 such asterminal device 204 in FIG. 2, base station 101 sets the rankinformation in the control information at 2, the MCSI and RV combinationof CW1 at “enable”, and the MCSI and RV combination of CW2 at “enable”.For a terminal device transmitting two CWs using port 7 to port 9 suchas terminal device 302 in FIG. 3, base station 101 sets the rankinformation in the control information at 3. For a terminal devicetransmitting two CWs using ports 7 to port 14 such as terminal device402 in FIG. 4, base station 101 sets the rank information in the controlinformation at 8. Thus, by having base station 101 and the terminaldevices maintain a common table in advance, and notifying the controlinformation from base station 101, the terminal device can shareinformation of ports used for transmitting a CW addressed to itself(port information).

In the control information format of a communication system according tothe present embodiment (downlink control information (DCI) format), basestation 101 can specify the port by a combination of informationindicating the rank (the number of spatial multiplex) and the parameterfor every CW (transmission parameter). In other words, by takingadvantage that the highest multiplex value of MU-MIMO is less than thatof SU-MIMO and restricting the port combination, base station 101 canspecify a port efficiently. Furthermore, by sharing the controlinformation format between SU-MIMO and MU-MIMO, base station 101 and theterminal device can carry out processing efficiently.

Particularly for a system that identifies control information of aplurality of different formats by blind decoding, the circuit complexityof the terminal device can be reduced since the types of formats forblind decoding can be reduced. Furthermore, since the relevant systemcan reduce the number of times of blind decoding, the processing of theterminal device can be reduced.

Thus, base station 101 multiplexes N (N is a natural number of 2 andabove) reference signals orthogonal to each other for transmission, andtransmits control information including information (first identifier)identifying the rank of a transmission signal addressed to a certainterminal device that is the communication destination and information(second identifier) identifying the transmission parameter of atransmission signal. The terminal device obtains a reference signalusing information identifying the rank and information identifying thetransmission parameter of a transmission signal. Accordingly, basestation 101 can specify a port with efficient signaling. Thus, basestation 101 and the terminal device can carry out effectivetransmission.

Second Embodiment

A second embodiment of the present invention will be describedhereinafter with reference to the drawings. The present embodimentcorresponds to the case of carrying out MU-MIMO using a sequence(quasi-orthogonal sequence, scramble sequence), in addition to the port.Although the description is based on the case of using aquasi-orthogonal sequence as the sequence, a similar effect can beachieved by carrying out processing similar to that set forth above evenfor a scramble sequence.

A CW addressed to a terminal device of which the rank is less than orequal to 2 is transmitted using port 7 or port 8. The base stationmultiplexes a CW addressed to two terminal devices at most at port 7 orport 8. The base station transmits the transmission signal addressed toeach terminal device in independent directivity patterns. At this stage,the base station multiplies RS by the sequence differing between theterminal devices. Accordingly, RS can readily be demultiplexed at theterminal device side.

The control information according to the present embodiment can berealized using information similar to the control information shown inFIG. 9. FIG. 11 represents an example of ports and sequencescorresponding to the control information according to the presentembodiment. Among the 8 states represented by the 3-bit rankinformation, state 1 and state 2 both indicate that the rank is rank 2or lower. For those of state 3 and above among the 8 states, the numberof each state corresponds to the rank number.

When the rank information is at state 1 or state 2, the base stationspecifies a port using the state allocated to the information for everyCW, in addition to the rank information. When one CW is to betransmitted to an arbitrary terminal device, the sets the MCSI and RVcombination of one CW at “disable” (combination indicatingnon-transmission) and the MCSI and RV combination of the other CW at“enable” (combination of arbitrary values that are not “disable”). Basedon the 1-bit NDI at the CW set at “disable” and whether the rankinformation is at state 1 or state 2, the base station specifies the twoports of port 7 and 8.

When two CWs are to be transmitted towards an arbitrary terminal device,the base station sets the MCSI and RV combination of both CWs at“enable”. The base station specifies the combination of port 7 and port8, or the combination of port 9 and port 10, depending upon whether therank information is at state 1 or state 2. Furthermore, base station 101specifies a sequence by state 1 indicating sequence 1 and by state 2indicating sequence 2. On part of the terminal device, first the rankinformation is confirmed. The terminal device obtains the sequencecorresponding to the state and further confirms the MCSI and RVcombination of CW1 and CW2 when the rank information is at state 1 orstate 2. When both are “enable”, the terminal device obtains the twoports information from the state of the rank information. If the MCSIand RV combination of one CW is “disable”, the terminal device confirmsthe NDI and SCID of the CW corresponding to “disable”, and obtains oneport information. Although FIG. 3 shows the case where CW1 is used intransmitting one CW towards one terminal device, the MCSI and RVcombination and the NDI of CW1 are to be replaced with those of CW2 whenCW2 is to be used. State 1 and state 2 can be shared between SU-MIMO andMU-MIMO.

When the rank information is at state 3 to state 8, the base stationspecifies the port combination using each state. By fixedly setting theemployed port for each rank of SU-MIMO by the base station, the rankinformation state and port combination can be set in one-to-onecorrespondence. Thus, the base station can suppress the number of bitsrequired for the control information.

Thus, in a communication system in which abuse station and terminaldevice carry out communication by SU-MIMO or MU-MIMO, the base stationmultiplies N reference signals orthogonal to each other orquasi-orthogonal to each other by a quasi-orthogonal sequence fortransmission, and transmits control information including information(first identifier) identifying the rank of a transmission signaladdressed to a certain terminal device that is the communicationdestination and information (second identifier) identifying thetransmission parameter of a transmission signal. The terminal deviceidentifies whether the reference signal is orthogonal orquasi-orthogonal from the information identifying the rank. When thereference signals are quasi-orthogonal, the terminal device uses theinformation identifying the rank and the information identifying thetransmission parameter of the transmission signal to obtain thereference signal and the quasi-orthogonal sequence. When the referencesignals are orthogonal, the terminal device obtains the reference signalusing the information identifying the rank. Accordingly, the basestation can specify a port and a quasi-orthogonal sequence withefficient signaling. Thus, the base station and terminal device cancarry out communication efficiently.

Third Embodiment

A third embodiment of the present invention will be describedhereinafter with reference to the drawings. The first embodiment wasdescribed based on a communication system with a base station supporting8 ports at most. The present embodiment is directed to a communicationsystem having a base station supporting 4 ports at most. FIG. 12represents an example of control information according to the presentembodiment. The base station supporting 4 ports at most in SU-MIMOnotifies each terminal device about control information includinginformation indicated in FIG. 12. Specifically, the control informationincludes, for each terminal device, 2 bits of rank information (firstidentifier) that is the information indicating the number of spatialmultiplex addressed to that terminal device, and 16 bits of information(second identifier) related to CW1 and CW2.

FIG. 13 shows an example of a correspondence table representing ofcontrol information and ports according to the present embodiment.Specifically, FIG. 13 represents an example of control information usedat the system carrying out MU-MIMO using ports 7 and 10 that are portsorthogonal to each other. Among the four states represented by two bitsof rank information, state 1 and state 2 both indicate that the rank isrank 2 or lower. For those of state 3 and above among the 8 states, thenumber of each state corresponds to the rank number. For thecorresponding relationship between rank information, information relatedto CW1. and CW2, and the port to be allocated (one or more of ports7-10), the correspondence similar to that of the first embodiment may beemployed.

FIG. 14 represents another example indicating ports corresponding tocontrol information according to the present embodiment. FIG. 14represents an example of control information used at the system carryingout MU-MIMO using ports 7 to 8 that are ports orthogonal to each otherand two types of quasi-orthogonal sequences. Among the four statesrepresented by two bits of rank information, state 1 and state 2 bothindicate that the rank is rank 2 or lower. For those of state 3 andabove among the 4 states, the number of each state corresponds to therank number. For the corresponding relationship between rankinformation, information related to CW1 and CW2, and the port to beallocated (one or more of ports 7-10), the correspondence similar tothat of the first embodiment may be employed.

By the base station combining information representing the rank andinformation representing the parameter for every CW in the controlinformation format of the communication system according to the presentembodiment, a port can be specified. In other words, by taking advantagethat the highest multiplex value of MU-MIMO is less than that of SU-MIMOand restricting the port combination, the base station can specify aport efficiently. Furthermore, by sharing the control information formatbetween SU-MIMO and MU-MIMO, the base station can carry out processingefficiently.

Fourth Embodiment

A fourth embodiment of the present invention will be describedhereinafter with reference to the drawings. in the present embodiment,the base station and terminal device according to the first to thirdembodiments set forth above will be described from the standpoint ofdevice configuration.

FIG. 15 schematically represents an example of a configuration of a basestation (transmission device) according to the present embodiment, Acoding unit 1501 applies rate mapping to each information data (bitsequence) for every CW sent from an upper layer 1510. A scrambling unit1502 multiplies each information data subjected to error correctingcoding and rate mapping by a scrambling code. A modulation unit 1503applies modulation processing such as PSK modulation, or QAM modulationto each transmission data multiplied by a scrambling code. A layermapping unit 1504 refers to port information to distribute a modulationsymbol sequence output from modulation unit 1503 for every layer. Eachlayer in SU-MIMO and MU-MIMO corresponds to each port. A referencesignal generation unit 1506 refers to the port information to generate areference signal sequence for every port. A precoding unit 1505 appliesprecoding processing to the modulation symbol sequence for every layerand precoding to the reference signal sequence for every port generatedat reference signal generation unit 1506, Accordingly, precoding unit1505 generates RS. More specifically, precoding unit 1505 multiplies themodulation symbol sequence or reference signal by a precoding sequence.

A control information generation unit 1511 uses the port information togenerate control information (downlink control information) described inthe first to third embodiments. A resource element mapping unit 1507maps the modulation symbol sequence precoded at precoding unit 1505, RS,and control information generated at control information generation unit1511 to a predetermined resource element. When a RS is to be mapped,resource element mapping unit 1507 can apply the multiplexing methodindicated in FIGS. 6-8 such that the RS for each port is orthogonal toeach other.

An OFDM signal generation unit 1508 converts the resource block groupoutput from resource element mapping unit 1507 into an OFDM signal. OFDMsignal generation unit 1508 transmits the OFDM signal obtained byconversion from transmission antenna 1509 as a downlink transmissionsignal.

FIG. 16 schematically represents an example of a configuration of aterminal device (reception device) according to the present embodiment.An OFDM signal demodulation unit 1602 applies OFDM demodulationprocessing to a downlink reception signal received at reception antenna1601 to output a resource block group.

A resource element dernapping unit 1603 demaps the control information.A control information acquirement unit 1611 obtains port informationfrom the control information. The obtained port information is set inthe terminal device. For obtaining port information from the controlinformation, the method described in the first to third embodiments isused. Then, resource element demapping unit 1603 refers to the portinformation to obtain RS from the resource element located at apredetermined position, and outputs the obtained RS to reference signalmeasurement unit 1610. Resource element demapping unit 1603 outputs anyreception signal at a resource element other than the resource elementhaving RS mapped to a filter unit 1604. Resource element dernapping unit1603 carries out processing corresponding to that carried out atresource element mapping unit 1507 in obtaining RS. More specifically,when TDM, FDM, CDM, or the like are applied such that the RS isorthogonal to each other for every port at resource element mapping unit1507, resource element demapping unit 1603 carries out demapping orinverse diffusion corresponding to the application.

Reference signal measurement unit 1610 measures the channel for eachport by multiplying the RS for each port output from resource elementdemapping unit 1603 by a sequence corresponding to the reference signalsequence for every port generated at reference signal generation unit1506 (the complex conjugate sequence of the reference signal sequence).Since RS is precoded in the transmission device, reference signalmeasurement unit 1610 will measure an equivalent channel includingprecoding in addition to the channel between the transmission antennaand reception antenna.

Filter unit 1604 subjects the reception signal output from resourceelement demapping unit 1603 to filtering. A filter unit 1604 furtherapplies the precoding corresponding to the precoding at precoding unit1505 to output a signal for every layer to a layer demapping unit 1605.Layer demapping unit 1605 applies a conjugation process corresponding tolayer mapping unit 1504 to convert the signal for every layer into asignal for every CW. A demodulation unit 1606 applies demodulationprocessing corresponding to the modulation processing at modulation unit1503 to the converted signal for every CW. A descrambling unit 1607multiples the signal for every CW subjected to demodulation processingby a complex conjugate of the scrambling code used at scrambling unit1502 (divide by the scrambling code). Then, decoding unit 1608 appliesrate demapping and error correction decoding to the signal for every CWhaving a complex conjugate multiplied to obtain information data forevery CW. Decoding unit 1608 transmits the Obtained information data forevery CW to upper layer 1609.

Filter unit 1604 applies, as filtering processing, zero forcing (ZF),minimum mean square error (MMSE), maximum likelihood detection (MID) orthe like to the reception signal for every reception antenna 1601 todetect a transmission signal for each layer (port) of FIG. 15.

Although the description is based on the case where MU-MIMO is carriedout using only orthogonal ports, transmission and reception processingcan be carried out by a similar configuration for MU-MIMO using aquasi-orthogonal sequence, In this case, quasi-orthogonal sequenceinformation is included in the port information. Reference signalgeneration unit 1506 multiplies in advance the quasi-orthogonal sequenceby a reference signal sequence, and resource element demapping unit 1603demaps the RS from the resource element, and descrambling, unit 1607carries out the processing of multiplying the complex conjugate of thequasi-orthogonal system subsequent to the demapping.

At a communication system including a transmission device and thereception device, the transmission device can specify a port bycombining information indicating the rank (multiplex value) withinformation indicating the parameter for every CW (transmissionparameter). By transmitting control information including informationindicating the rank and information indicating the parameter for everyCW from the transmission device to the reception device, informationrelated to the reference signal can be shared between the transmitterdevice and reception device. In other words, the transmission device canspecify a port corresponding to a reference signal efficiently by takingadvantage that the highest multiplex value of MU-MIMO is less than thatof SU-MIMO, and limiting the combination of a port corresponding to areference signal.

In the case where MU-MIMO is carried out using a quasi-orthogonalsequence, the terminal device may have compatibility with a conventionalcommunication system that multiplexes a reference signal multiplied bytwo types of quasi-orthogonal codes via two orthogonal first ports fortransmission.

Each of the embodiments is described based on, but not limited to usinga resource element and resource block as the mapping unit oftransmission data and RS, and using a subframe and radio frame as thetransmission unit in the time direction. A similar effect can beachieved by using a region constituted of an arbitrary frequency andtime, and the time unit instead.

Each embodiment has been described based on, but not limited to the casewhere SU-MIMO and MU-MIMO are supported. For example, in a communicationsystem supporting only SU-MIMO, the base station can specify a portcorresponding to a reference signal of favorable performance at a lowrank by virtue of the signaling described in each of the embodiments setforth above. Therefore, effective communication can be carried out bythe relevant configuration.

Each embodiment has been described based on, but not limited to the casewhere demodulation is carried out using a RS subjected to precoding, andusing a port equivalent to the layer of MIMO as the port correspondingto the RS subjected to precoding. A similar effect can he achieved byapplying the present invention to a port corresponding to referencesignals differing from each other. For example, an unprecoded RS insteadof a precoded RS can be used, and a port equivalent to the output endsubsequent to precoding or a port equivalent to a physical antenna (or acombination of physical antenna) can be used.

The program operated at a mobile station device and base stationaccording to the present invention is a program controlling a CPU or thelike (a program for operating a computer) so as to realize the functionof the embodiments set forth above involved in the present invention.The information handled at these devices are temporarily stored in a RAMduring processing, and then stored in various ROM or HDD to be read outby the CPU, as necessary, for correction and writing. The storage mediumfor storing the program may be any of a semiconductor medium (forexample, ROM, non-volatile memory card), an optical recording medium(for example, DVD, MO, MD, CD, BD), a magnetic recording medium (forexample, magnetic tape, flexible disc) or the like. In addition torealizing the functions of the embodiment set forth above by executing aloaded program, the functions of the present invention may be realizedby a process according to an operating system or another applicationprogram or the like, based on the commands of that program.

Further, the recording medium is anon-transitory medium storing therelevant program in a computer-readable manner. As used herein, aprogram includes, not only a program that can be executed directly by aCPU, but a program of a source program format, a program subjected tocompression, encrypted program, and the like.

When distributing to be available on the market, the program can bestored in a portable recording medium for distribution, or may betransferred to a server computer connected via a network such as theInternet. In this case, the storage device of the server computer isincluded in the present invention.

The mobile station device and base station in the embodiment set forthabove may be partially or completely realized as an LSI that istypically an integrated circuit. The mobile station device and eachfunction block of the base station may be provided individually inchips, or these functions may be integrated partially or entirely in achip. The means for an integrated circuit is not limited LSI, and may berealized by a dedicated circuit, or a general-purpose processor. Whendevelopment in the semiconductor art sees the approach of achieving anintegrated circuit replacing an LSI, an integrated circuit by suchapproach may be employed.

<Appendix>

(1) An aspect of the present invention is directed to a transmissiondevice transmitting at least one transmission data using spatialmultiplex transmission. The transmission device includes a controlinformation generation unit (1511) generating, based on a referencesignal transmitted together with said transmission data, controlinformation including spatial multiplex information indicating thenumber of transmission data spatially multiplexed and informationindicating a parameter related to said transmission data, and atransmission unit (1508, 1509) transmitting said reference signal andsaid control information.

(2) Preferably, the information indicating a parameter related to saidtransmission data is control information indicating the modulationscheme and code rate for said transmission data, control informationindicating a puncturing pattern for said transmission data, andinformation indicating whether the transmission of said transmissiondata is the initial delivery or not.

(3) Preferably, said transmission data is downlink transmission data.Said reference signal is a signal for demodulating a physical downlinkshared channel in which said downlink transmission data is mapped.

(4) Another aspect of the present invention is directed to a receptiondevice receiving at least one transmission data using spatial multiplextransmission. The reception device includes a reception unit (1601,1602) receiving control information including spatial multiplexinformation indicating the number of transmission data spatiallymultiplexed and information indicating a parameter related to saidtransmission data, and a reference signal, and an identification unit(1603) identifying said reference signal using said control information.

(5) Preferably, said transmission data is downlink transmission data.Said reception device further includes a demodulation unit (1606)demodulating a physical downlink shared channel in which said downlinktransmission data is mapped using said identified reference signal.

(6) Still another aspect of the present invention is directed to acommunication system in which at least one transmission data istransmitted from a transmission device to a reception device usingspatial multiplex transmission. Said transmission device transmitscontrol information including spatial multiplex information indicatingthe number of transmission data spatially multiplexed and informationindicating a parameter related to said transmission data, and areference signal. Said reception device identifies said reference signalusing said control information.

(7) A still further aspect of the present invention is directed to acommunication method at a transmission device transmitting at least onetransmission data using spatial multiplex transmission. Thecommunication method includes the steps of: said transmission devicegenerating, based on a reference signal transmitted together with saidtransmission data, control information including spatial multiplexinformation indicating the number of transmission data spatiallymultiplexed and information indicating a parameter related to saidtransmission data, and said transmission device transmitting saidreference signal and said control information.

(8) A still further aspect of the present invention is directed to acommunication method at a reception device receiving at least onetransmission data transmitted using spatial multiplex transmission. Thecommunication method includes the steps of: said reception devicereceiving control information including spatial multiplex informationindicating the number of transmission data spatially multiplexed andinformation indicating a parameter related to said transmission data,and a reference signal, and said reception device identifying saidreference signal using said control information.

Although the embodiments of the present invention has been described indetail with reference to the drawings, it is to be understood that thespecific configuration is not limited by embodiments disclosed, and isintended to include any design or the like within the scope and meaningequivalent to the terms of the claims in the present invention.

INDUSTRIAL APPLICABILITY

The present invention is suitable used in a radio transmission device, aradio reception device, and a radio communication system and radiocommunication method.

REFERENCE SIGNS LIST

101 base station; 102-105, 202-204, 302, 402 terminal device; 106-109,205-208, 303, 304, 403, 404 code word; 601, 701, 801, 802 resourceelement; 1501 coding unit; 1502 scrambling unit; 1503 modulation unit;1504 layer mapping unit; 1505 precoding unit; 1506 reference signalgeneration unit; 1507 resource element mapping unit; 1508 OFDM signalgeneration unit; 1509 transmission antenna; 1510 upper layer; 1511control information generation unit; 1601 reception antenna; 1602 OFDMsignal demodulation unit; 1603 resource element demapping unit; 1604filter unit; 1605 layer demapping unit; 1606 demodulation unit; 1607descrambling unit; 1608 decoding unit; 1609 upper layer; 1610 referencesignal measurement unit; 1611 control information acquirement unit;1701, 1801, 1901 base station; 1702, 1802, 1803, 1902, 1903 terminaldevice; 1703, 1804, 1805, 1904, 1905 code word; 1906, 1907 directivitypattern.

1. A base station device configured to communicate with a terminaldevice, the base station device comprising: control informationgeneration circuitry configured to generate control informationincluding 3-bit information, the 3-bit information indicating at leastone port, one or less scrambling identity and the number of layers, andtransmission circuitry configured to transmit to the terminal device aphysical downlink shared channel, a reference signal for demodulation ofthe physical downlink shared channel, and the control information,wherein, in a case that two codewords are mapped to the physicaldownlink shared channel, among a first value to an eighth valueindicated by the 3-bit information, the third value to the eighth valueindicate that the number of layers is from 3 to 8 respectively, and thefirst value and the second value indicate that the number of layers isequal to 2, and the first value indicates that the scrambling identityfor the reference signal is equal to 0 and the second value indicatesthat the scrambling identity is equal to
 1. 2. A terminal deviceconfigured to communicate with a transmission unit, said terminal devicecomprising: reception circuitry configured to receive from the basestation device a physical downlink shared channel, a reference signalfor demodulation of the physical downlink shared channel, and a controlinformation which includes 3-bit information, the 3-bit informationindicating at least one port, one or less scrambling identity and thenumber of layers, wherein, in a case that two codewords are mapped tothe physical downlink shared channel, among a first value to an eighthvalue indicated by the 3-bit information, the third value to the eighthvalue indicate that the number of layers is from 3 to 8 respectively,and the first value and the second value indicate that the number oflayers is equal to 2, and the first value indicates that the scramblingidentity for the reference signal is equal to 0 and the second valueindicates that the scrambling identity is equal to
 1. 3. A method usedat a base station device which is configured to communicate with a.terminal device, the method comprising: generating, by controlinformation generation circuitry, control information including 3-bitinformation, the 3-bit information indicating at least one port, one orless scrambling identity and the number of layers, and transmitting, bytransmit circuitry, a physical downlink shared channel, a referencesignal for demodulation of the physical downlink shared channel, and thecontrol information, wherein, in a case that two codewords are mapped tothe physical downlink shared channel, among a first value to an eighthvalue indicated by the 3-bit information, the third value to the eighthvalue indicate that the number of layers is from 3 to 8 respectively,and the first value and the second value indicate that the number oflayers is equal to 2, and the first value indicates that the scramblingidentity for the reference signal is equal to 0 and the second valueindicates that the scrambling identity is equal to
 1. 4. A method usedat a terminal device which is configured to communicate with a basestation device, the method comprising: receiving, by receptioncircuitry, a physical downlink shared channel, a reference signal fordemodulation of the physical downlink shared channel, and a controlinformation including 3-bit information, the 3-bit informationindicating at least one port, one or less scrambling identity and thenumber of layers, wherein, in a case that two codewords are mapped tothe physical downlink shared channel, among a first value to an eighthvalue indicated by the 3-bit information, the third value to the eighthvalue indicate that the number of layers is from 3 to 8 respectively,and the first value and the second value indicate that the number oflayers is equal to 2, and the first value indicates that the scramblingidentity for the reference signal is equal to 0 and the second valueindicates that the scrambling identity is equal to 1.